Our general goal is to understand how living organisms detect and respond to changes in their environment. We are focusing on bacterial chemotaxis, the process by which bacteria migrate to higher concentrations of attractment, such as amino acids or sugars. We want to identify the biochemical changes that underlie chemotaxis and reproduce these in vitro. We have purified the methyltransferase that is responsible for methylating certain integral membrane proteins (called MCPs) following exposure of Bacillus subtilis to attractant. We are identifying, purifying and characterizing certain modifying proteins. We have identified a methylesterase that removes methyl groups from these proteins when attractant is diluted away, and expect to purify and characterize it and associated modifying proteins. There is evidence that it forms a complex of 180,000 daltons. We will be characterizing the role of many other methylated proteins, besides the ones methylated by the purified methyltransferase in conjunction with modifying factors, proteins to which methyl groups are transferred from the MCPs. Finally, we will be evaluating the role of cyclic GMP and Ca ions in chemotaxis and its effect on the methyltransferase and methylesterase reactions.